Author Topic: SpaceX Dragon XL  (Read 219288 times)

Online Robotbeat

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Re: SpaceX Dragon XL
« Reply #120 on: 03/28/2020 01:33 pm »
I've been wondering about the FH upmass so I checked SpaceX's web site. It is listed as 63,800kg or 140,660 lb to LEO and 16,800kg or 37,040 lb to Mars. I'm guessing that the mass numbers to Gateway are something in between. That seems like enough upmass capability to satisfy the needs of this mission. The payload just needs maneuvering thrusters like all Dragons before it.

Well, it needs some DeltaV for lunar orbit insertion and departure. It won't be anywhere near whats needed for TLI levels but still significantly more than what Dragon1+2 need to take a trip round the ISS in LEO and then reenter.
What is the delta v needed for Dragon 1 & 2 today?
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

To the maximum extent practicable, the Federal Government shall plan missions to accommodate the space transportation services capabilities of United States commercial providers. US law http://goo.gl/YZYNt0

Offline jarmumd

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Re: SpaceX Dragon XL
« Reply #121 on: 03/28/2020 01:46 pm »
If it is supposed to transfer both pressurized and unpressurized cargo, how could it have docking at both ends?

Also, SpaceX would need to build their own IDSS passive docking port.  Contrary to popular belief, the current system does not have the equipment to act as a passive for other vehicles to dock (ie not androgynous).  Unless someone specifically asked for that capability, that's $$ to develop and certify.  Not to mention, we are going to the moon, mass is critical, and docking ports (and the structure they need to support them) are heavy! 

Offline Ronsmytheiii

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Re: SpaceX Dragon XL
« Reply #122 on: 03/28/2020 01:52 pm »
My questions are:
1)  Is the cargo volume the same or larger than cargo D2?
2) Will part of that 5t of cargo include propellent for transfer?

Volume is substantially larger than cargo D2.
No propellant for transfer.

This is NOT Progress-on-steroids. More like Cygnus with unpressurized cargo capabilities.

Or like the TKS FGB modules?

https://en.wikipedia.org/wiki/Functional_Cargo_Block

Offline Ronsmytheiii

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Re: SpaceX Dragon XL
« Reply #123 on: 03/28/2020 01:56 pm »
I've been wondering about the FH upmass so I checked SpaceX's web site. It is listed as 63,800kg or 140,660 lb to LEO and 16,800kg or 37,040 lb to Mars. I'm guessing that the mass numbers to Gateway are something in between. That seems like enough upmass capability to satisfy the needs of this mission. The payload just needs maneuvering thrusters like all Dragons before it.

Well, it needs some DeltaV for lunar orbit insertion and departure. It won't be anywhere near whats needed for TLI levels but still significantly more than what Dragon1+2 need to take a trip round the ISS in LEO and then reenter.


Remember the Gateway will be in lunar near-rectilinear halo orbit (NRHO) which has lower delta-V requirements than a conventional low lunar orbit.

Offline yg1968

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Re: SpaceX Dragon XL
« Reply #124 on: 03/28/2020 02:06 pm »
If NASA requires it. There could be a Dragon XL variant with a grappling fixture and a full size CBM port with minor modification.

On that subject and as you probably already know, Canada will be building a robotic arm for Gateway and this arm would be delivered by Dragon XL.

https://www.cbc.ca/news/technology/canada-lunar-gateway-1.5037522

Quote from: NASA (Attachment_01_GLS_SOW_Annex_A)
1.0 The Contractor shall deliver the following DSXR [Deep Space Extravehicular Robotic System] items as unpressurized cargo to Gateway as part of one or more launch packages

https://forum.nasaspaceflight.com/index.php?topic=48353.msg2018139#msg2018139

Which is exactly why there is a grapple fixture on the side of Dragon XL. The deep space Canadarm will "walk" itself off the vehicle, onto the Gateway. The first step it takes from its stowed position is onto a grapple fixture on the side of Dragon XL.

Yes (and I just noticed it now), this was a NASA requirement:

Quote from: NASA (Attachment_03_GLS-RQMT-001_Gateway_Logistics_Services_Requirements)
L3-GLS-1111 Robotic Arm Walk-Off

The Logistics Vehicle that delivers the Robotic Arm shall support Robotic Arm selfdeployment and walk-off onto the Gateway.

Rationale: The Robotic Arm delivery mission concept requires that the Logistics Vehicle provide the power, data, attach points, attachment fixtures, and computational resources necessary for the arm system to activate and deploy itself from the Logistics Vehicle and onto the Gateway.

« Last Edit: 03/28/2020 03:34 pm by yg1968 »

Offline omelet1978

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Re: SpaceX Dragon XL
« Reply #125 on: 03/28/2020 02:08 pm »
Is everyone under the assumption that the Falcon Heavy will be used with an expendable center core and the two side boosters being recovered?

The reason I ask this is that doing that only reduces the Falcon Heavy's lift capability by about 10% and you get to re-use the Falcon 9 boosters. I'd imagine SpaceX is not going to be wanting to lose 2 Falcon 9 Block 5 reusable rockets every time they launch cargo to the Gateway. I'm very happy by this news since I think the Falcon Heavy needs to be utilized as much as possible for the next few years.

Offline nacnud

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Re: SpaceX Dragon XL
« Reply #126 on: 03/28/2020 02:14 pm »
Just from a configuration point of view it would be relatively easy to add a second docking port. Just have it covered in transit by the exposed cargo. Once that is unloaded the port would be revealed.

There is no point unless it is really needed as it adds weight and cost but if you wanted a DOS like station...   

Offline Jimmy Murdok

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Re: SpaceX Dragon XL
« Reply #127 on: 03/28/2020 02:21 pm »
Can we assume that the solar panels use the same design as for Dragon 1?

Offline woods170

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Re: SpaceX Dragon XL
« Reply #128 on: 03/28/2020 02:27 pm »
Can we assume that the solar panels use the same design as for Dragon 1?


Basically same basic design with regards to carrier panels, hinges, gimbal, wiring, electronics and deployment mechanism. Hardened PV cells though.
Lots and lots of commonality with Dragon 1 solar arrays. Keeps cost down.
« Last Edit: 03/28/2020 02:28 pm by woods170 »

Offline yg1968

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Re: SpaceX Dragon XL
« Reply #129 on: 03/28/2020 02:30 pm »
If NASA requires it. There could be a Dragon XL variant with a grappling fixture and a full size CBM port with minor modification.

On that subject and as you probably already know, Canada will be building a robotic arm for Gateway and this arm would be delivered by Dragon XL.

https://www.cbc.ca/news/technology/canada-lunar-gateway-1.5037522

Was thinking of contingency delivery of really bulky cargo to the ISS that requires a full size CBM hatch.

If I am reading this correctly, once the robotic arm is installed on Gateway, a berthing option is also required (however, see the post below mine on berthing operations vs berthing mechanisms; the requirements below only require berthing operations to be possible, not a CBM):

Quote from: NASA (Attachment_03_GLS-RQMT-001_Gateway_Logistics_Services_Requirements)
3.10 EXTRAVEHICULAR ROBOTICS COMPATIBILITY

The requirements in this section are applicable to Logistics Vehicles which will dock to Gateway when Extravehicular Robotics capability has been established. [...]

Rationale: The capability for a docked Logistics Module to be relocated to another docking port via the Gateway EVR system reduces Gateway risk and preserves LM consumables.

L3-GLS-1119 Berthing Grapple Fixture Accommodation

The Logistics Module shall have a radially-installed Extravehicular Robotics-compatible Grapple Fixture located within 3.5m (11.5ft) of the docking/berthing port center to enable berthing to Gateway. [...]

Rationale: Gateway operations will need the capability to relocate and berth visiting vehicles using the Robotic Arm. Constraining the relative location of the Grapple Fixture permits manipulator configurations that can provide sufficient push force to overcome resistance forces for all berthing scenarios

https://forum.nasaspaceflight.com/index.php?topic=48353.msg2018139#msg2018139

Edit: to take into account the post below.
« Last Edit: 03/28/2020 03:16 pm by yg1968 »

Offline jarmumd

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Re: SpaceX Dragon XL
« Reply #130 on: 03/28/2020 02:39 pm »
A couple points:

Docking and Berthing are operations, docking is done under spacecraft control, berthing done with an arm under astronaut control

There are also Docking and Berthing mechanisms, ie IDSS vs CBM.

Confusing point that a Docking system could be berthed (I don't think anyone quite knows how to do this yet), but a Berthing system cannot be docked.

Also, adding a CBM to Dragon XL would be a massive redesign.  Possible you could make an adapter, but it would probably be a very expensive adapter.

Offline edkyle99

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Re: SpaceX Dragon XL
« Reply #131 on: 03/28/2020 02:42 pm »
I'm guessing these have to be fully expendable Falcon Heavy launches, to get 5 tonnes of cargo to lunar orbit in a spacecraft that has to weigh 5-times-something tonnes - maybe 20 tonnes at TLI with about 1/4th of that mass needed for lunar orbit insertion.

 - Ed Kyle

Can't give you the exact numbers but my source says your mass estimate for the vehicle is way off. As in: your mass estimate for the vehicle is way too high.
Is your source counting the mass needed for lunar orbit insertion?  Maybe there is an entirely separate stage, or maybe the Falcon upper stage does some of the work.  Consider this example.  Apollo 17 entered trans-lunar injection at 46.8 tonnes.  After its lunar insertion burn, the CSM/LM combination weighed 34.72 tonnes, using 26% of the TLI mass for that maneuver. 

So, if payload is 5 metric tons (tonnes)(SpaceX number), then the spacecraft plus payload in lunar orbit has to weigh maybe 2.1 to 2.75 times as much (see Cygnus, ATV, HTV, etc), which gets us to 10.5 to 13.75 tonnes.  That mass divided by 0.74 for the lunar insertion gives 14.2 to 18.6 tonnes at trans-lunar injection. 

Of course this assumes a low lunar orbit delta-v maneuver, which I guess isn't happening in this case.  From TLI to the Gateway NRHO using a lunar flyby would be something like 420 m/s delta-v, which for a 300 sec ISP Draco assumption would I think require about 13.5% of total TLI mass for the burns, resulting in a 12 to 15.9 tonne TLI mass range.

This seems to me to be in the range requiring an expendable Falcon Heavy based on published and proven capabilities.  SpaceX may be able to do downrange side booster recovery and achieve this result (while expending the center core), or some of it, but downrange recovery of two cores simultaneously on a Heavy flight has yet to be demonstrated.

 - Ed Kyle 
« Last Edit: 03/28/2020 11:12 pm by edkyle99 »

Offline Kaputnik

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Re: SpaceX Dragon XL
« Reply #132 on: 03/28/2020 02:57 pm »
Re: disposal
Don't worry too much about long term space junk around the moon. Lunar orbit are pretty unstable due to mascons so nothing survives in orbit there more than a few years without active manoeuvring (which requires delta-v).
"I don't care what anything was DESIGNED to do, I care about what it CAN do"- Gene Kranz

Offline baldusi

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Re: SpaceX Dragon XL
« Reply #133 on: 03/28/2020 03:24 pm »
If I am reading this correctly, once the robotic arm is installed on Gateway, a berthing option is also required (however, see the post below mine on berthing operations vs berthing mechanisms; the requirements below only require berthing operations to be possible, not a CBM):

Quote from: NASA (Attachment_03_GLS-RQMT-001_Gateway_Logistics_Services_Requirements)
3.10 EXTRAVEHICULAR ROBOTICS COMPATIBILITY

The requirements in this section are applicable to Logistics Vehicles which will dock to Gateway when Extravehicular Robotics capability has been established. [...]

Rationale: The capability for a docked Logistics Module to be relocated to another docking port via the Gateway EVR system reduces Gateway risk and preserves LM consumables.

L3-GLS-1119 Berthing Grapple Fixture Accommodation

The Logistics Module shall have a radially-installed Extravehicular Robotics-compatible Grapple Fixture located within 3.5m (11.5ft) of the docking/berthing port center to enable berthing to Gateway. [...]

Rationale: Gateway operations will need the capability to relocate and berth visiting vehicles using the Robotic Arm. Constraining the relative location of the Grapple Fixture permits manipulator configurations that can provide sufficient push force to overcome resistance forces for all berthing scenarios

https://forum.nasaspaceflight.com/index.php?topic=48353.msg2018139#msg2018139

Edit: to take into account the post below.
I've underlined the critical part. Docking requires to take a hit from the visiting vehicle. This is both a stress (mostly taken by the docking mechanism), and then you have to compensate the delta-v change. So, with berthing, even using IDA, APAS or any other type of IDSS-derived docking system, you save fuel on the gateway AND you reduce the stress.

Offline jak Kennedy

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Re: SpaceX Dragon XL
« Reply #134 on: 03/28/2020 03:28 pm »
Would Dragon XL require the future elongated FH fairing?
I'd assume that (like current Dragon), it is its own fairing, likely with a larger jettisoned nose cap a la Dragon 1.

Then why are the control thrusters sticking outside the trunk? Perhaps this is just a rough render for now but strange the RCS thrusters are not placed inside wether or not it uses a fairing.
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Offline yg1968

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Re: SpaceX Dragon XL
« Reply #135 on: 03/28/2020 03:36 pm »
Would Dragon XL require the future elongated FH fairing?
I'd assume that (like current Dragon), it is its own fairing, likely with a larger jettisoned nose cap a la Dragon 1.

Then why are the control thrusters sticking outside the trunk? Perhaps this is just a rough render for now but strange the RCS thrusters are not placed inside wether or not it uses a fairing.

That was early speculation, we now know that it will be in a regular FH fairing. See Woods170's post above.

Online Comga

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Re: SpaceX Dragon XL
« Reply #136 on: 03/28/2020 03:43 pm »
[...]
And on the way back in "garbage truck" mode... take a month or two to reenter in a controlled manner.
[...]

Why would it need to reenter for disposal? BEO or Moon-crashing would most probably be cheaper, delta-v wise.

It's always bothered me when "we" leave our "stuff" in places they should not be left... JMHO...
I smile every time a spacecraft saves enough fuel, or puts itself in a <90day to re-entry orbit...to clean up after itself... 
Delta-v be damned... figure out how to make it work before you launch it... or just don't...
Sacrifice payload or as a last resort, expend the rocket if you have to...
Because someday, someone will have to clean up the mess we have made over the last 60+years in space...
Again... JMHO...  ;)

Space is big, I mean really big.

You can’t believe how mind bogglingly big it is!
I mean, you may think it’s a long way down the street to the Chemist, but that’s just peanuts compared to space!
Eventually it gets down to things you can use...

PEOPLE!
That’s the opening of The Hitchhiker’s Guide To The Galaxy, the book with “Don’t Panic” on its cover in the books, TV show, and radio drama of the same name.
(or as close as I can come from memory after 40 years)

It’s not a policy proposal or even an opinion on what they/SpaceX/NASA should do.

Lighten up!
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Offline yg1968

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Re: SpaceX Dragon XL
« Reply #137 on: 03/28/2020 03:44 pm »
The Dragon XL is expected to be docked for 6 months at Gateway. See below:

Quote from: NASA (Attachment_01_GLS_SOW)
4.1 REQUIRED CAPABILITY

The Contractor shall provide for the safe integration, transport and stowage of NASA-provided cargo, both pressurized and unpressurized, to the Gateway and disposal of NASA-provided cargo upon departure from the Gateway.  The Contractor’s logistics vehicle shall be designed to remain docked to Gateway for one (1) year, with efficient crew access to stowage and payloads but the capability to remain longer than one year should also be considered. The nominal mission docked duration is expected to be six months. . The common launch vehicle configuration shall have one (1) successful flight prior to the GLS Missions.
 
https://forum.nasaspaceflight.com/index.php?topic=48353.msg2018139#msg2018139
« Last Edit: 03/28/2020 03:47 pm by yg1968 »

Offline Ronsmytheiii

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Re: SpaceX Dragon XL
« Reply #138 on: 03/28/2020 03:44 pm »
Confusing point that a Docking system could be berthed (I don't think anyone quite knows how to do this yet)

Actually we do know, since the MRM-1 module launched to the ISS on STS-132 and attached using the SSRMS. mRM-1 used a “hybrid” docking system.


Offline Jorge

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Re: SpaceX Dragon XL
« Reply #139 on: 03/28/2020 03:54 pm »
Confusing point that a Docking system could be berthed (I don't think anyone quite knows how to do this yet)

Actually we do know, since the MRM-1 module launched to the ISS on STS-132 and attached using the SSRMS. mRM-1 used a “hybrid” docking system.



On STS-74, the Mir Docking Module was berthed to the shuttle APAS using the shuttle RMS before the shuttle/DM docked with Mir.
On STS-88, Node 1 was berthed to the shuttle APAS using the shuttle RMS, then FGB was berthed to Node 1 APAS using the shuttle RMS, to form the initial ISS complex.

Berthing a vehicle/module using a docking mechanism has multiple precedents.
JRF

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